Most temperature related reference generations are in the voltage domain, which means that reference voltages rather than reference currents are generated, see for example "CMOS analog circuit design" by P. Allen and D. Holberg, Holt, Rinehart and Winston Inc., 1987. In some applications such as driving laser diodes, currents are needed rather than voltages. Though the voltage references could be generated and then the currents could be derived through a resistor, the temperature dependent resistance would make the reference voltage generation relatively complicated in order to cope with the temperature dependency of the resistors.
In the international application published under the PCT: WO 95/22093 there is disclosed and shown a reference circuit, which has a controlled temperature dependence, where a reference circuit for producing an output reference current has an arbitrary predetermined temperature dependence. By adding a few currents with different temperature coefficents a current with desired temperature dependence can be achieved. Even if there is disclosed an invention of generating a current with controlled temperature dependence in the integrated form, the main idea is to generate a controlled gate source voltage, which is used to generate the drain current with controlled temperature dependence. The operation philosophy will therefore be first to generate a voltage and then at the final stage to convert the voltage into a current.